Surfaces of components often have to have contaminants removed from them for application of or in intermediate steps of various processes. The contaminants may be grains of dust, oil or grease films or corrosion products on the surface of the component. Simple wiping or dry ice blasting processes are known as prior art. However, if a recess or a crack is to be cleaned, it is necessary to employ more complex processes. This is done for example by fluoride ion cleaning (FIC), hydrogen annealing or salt bath cleaning. In these processes, which entail considerable outlay on apparatus, the surfaces which are not to be cleaned are in some cases also adversely affected to a significant extent.
Plasma-enhanced vacuum etching processes carried out on components as part of known PVD or CVD coating processes immediately prior to the vapor deposition are known. The basic principle of this surface treatment is the atomization or sputtering of adhering contaminants and of the upper atom layers of the material to be removed to form particles of atomic size by bombardment with inert gas ions. The very finely atomized contaminant has, as it were, passed into the vapor phase and can be sucked out. Plasmas of this type can be achieved by coupling suitable electrode arrangements to high-voltage/radiofrequency generators. However, these processes are only employed to clean planar surfaces.
EP 0 313 855 A2 discloses a process for generating a gas plasma in which the voltage is controlled to a specific value.
EP 0 740 989 A2 discloses a method for cleaning a vulcanization mold, in which a plasma flow is generated.